How can someone pay zakah who is owed money, does business and owes debts?

No zakaah is required on wealth that is given as a waqf to help people get married

Can he take back the zakaah of his wealth if he gave it to a poor person then found out that he did not need it?

His deputy gave the zakaah of his wealth in the form of foodstuff; is that acceptable or does he have to give it again?

He appointed his sister to distribute his zakaah but she refused to do it; does he have to give it again?

He gave him a bag of rice; can he give zakat al-fitr from it?

Is it permissible to give items as zakah instead of cash?

He has some goods and some profits – how should he work out his zakaah?

Is it permissible for one who has taken out a riba-based loan to receive zakaah in order to pay off his debt?

He has repented from not praying or giving zakah; does he have to make them up?